Pumping of concrete



March 11,1958

2 Sheets-Sheet 1 Filed Jan. 1'7, 1955 Inventor y WM M Attorney 5 March11, 1958 A. N. EDE

PUMPING OF CONCRETE 2 SheetsSheet 2 Filed Jan, 17, 1955 W Em M Attorney5 United States Patent PUMPING or CONCRETE Ainsley-Neville Ede,Cambridge, England, assignor to NationalResearch DevelopmentCorporation, London, England, a corporation Application January 17,1955, Serial No. 482,315

Claims priority, application Great Britain January 20, 1954,

r 14 Claims. (Cl. 25-16) inventionjrelates to the pumping of wetconcrete in the plastic state, and may be applied for example to thepropulsion of a continuous stream of concrete through a' closed pipe, orto its consolidation under pressure in a :mould, or to the forcing ofthe concrete through an extrusion device for the production of anextruded article. The. invention is particularly though not exclusivelyapplicable to .the continuous extrusion of concrete pipes underground bymeans of a mole plough in combination with an extruder- According to oneaspect of the present invention, a pump for pumpinga column of wetconcrete in the plastic state'includes a hollow tube having an inlet ator near one end and having its other end open as an outlet leading to areceiver, vmeans for supplying the concrete to the interior; of the tubevia the inlet, and means for causing the tubelto reciprocate in theaxial direction, the linear acceleration given to the tube during itsmovement on its forward stroke towards the receiver being so low that'there is no slip or substantially no slip between the tube and theconcrete contained therein during thewhole or the majority of theforward stroke, whilst durin'g "the.majority of the return stroke thelinear acceleration given to the tube is so great that there is slipbetween. the wall of the tube and the concrete contained therein duetothe inertia of the concrete. Thus the concretewill be progressivelyadvanced or pumped towards the receiver through the bore of the tube.

thepurposes of the present invention the term wet-concrete is used toinclude any mixture of cement ands and with, gravel and/or otheraggregate, containing water in any quantity up to saturation, and withor without entrained air and/or additives for producing foaming orentrained gases or for lubrication purposes.

Such wet ,concrete, when in the plastic state prior to the setting ofthecement, exhibits two physical characteristics which are of importance tothe present invention. Firstly appreciable static friction can bedeveloped be tw'eedthe concrete and the walls of a containeror any othertangential surface, and such friction increases with the pressureexerted by the material on the surface in the zone of friction.Secondly, the material when subjected to compressivestress in onedirection is capable of exertingac'o'rresponding though smaller stressin a transverse.

vented by a container which will then be subjected to direction. Forexample if a cylindrical specimen is com pressed'axially it tends toexpand radially unless preradial pressure by the mixture.

Thesecharacteristics are made use of in the present inven'tionyin whichthe friction between the wall of the reciprocating tube and the concretetherein during the forward stroke of the. tube towards the receivertends to producea pressure gradient in the column of concrete 2,825,955Patented Mar. 11, 1958 in the tube, the pressure increasingprogressively towards the outlet end ofthe tube. The increased pressurein turn tends to increase the friction between the concrete and thetube, so that the effect is cumulative and so that the Wholecolum'nofconcrete, or the bulk of it, tends to move solidly with thetubetowards the receiver during this stroke.

During the return stroke however the acceleration of. the tube is so,rapid .thatthe available friction cannot move the concrete-column backwith an thin'g-likev the same acceleration due to its inertia, and slipoccurs. There is thus a steady progression of the column of con.

crete through the tube towards the receiver, accompanied by an increasedpressure adjacent the receiver.

The present invention according to another of its aspects comprises amethod of pumping wet concrete by.

supplyingwet concrete in the plastic state to the interior of a hollowtube via an inlet at one end whilst continuously causing the tube toreciprocate in the axial direction, the other end of the tube being openand leading to a receiver, in which the linear acceleration given to thetube during its forward stroke towards the receiver is so low that thereis no slip or substantially no slip.

between the tubeandthe. concrete contained in it during the whole or themajority of the forward stroke, Whilst during the majority of the returnstroke the linear acceleration given to the tube is so great that thereis slip between the wall of the tube and the concrete contained thereindue to the, inertia of the concrete.

The receiver may bein the form of a pipe or flexible hose or the likethrough which the concrete is to be transmitted to the place or mould inwhich it is to be poured and consolidated to a required shape orsection, or it may extruded into the tunnel produced by forcing themole,

plough through the ground. The method of supplying the concrete to theextruder by means of the present invention is particularly convenient inthis application, as the moving parts needed for pumping the concretethrough the extruder are reduced in number and the extruding cycle canbe performed at a rate controlled in accordance with the rate of advanceof the mole plough. It is found that the pumping method of the presentinvention works particularly well using the coarse, rather dry mixeswhich are suitable for permeable concrete drain pipes.

In some cases it may be necessary to feed the concrete positively to theinlet end of the reciprocating tube, as-

by a gravity feed, with or without a vibratory action, to ensurecontinuity.

each advancing stroke without outside assistance.

Whilst the reciprocating tube will generally be of uniform cross-sectionfrom end to end, for example of cylin- I drical cross-section, in somecases it may be desirable In other cases where the mixture is such as tobe able to transmit small tensile stresses, the concrete may be able to.draw itself into the tube during For the, purpose of manufacturingcertain extruded sections, a core or cores may be positioned inside thereciprocating tube, extending along the whole or a part of its length.

When the invention is employed for the propulsion of concrete through apipe or hose, additional water may be introduced into the material inthe hose at a point downstream from the outlet from the reciprocatingtube and sufliciently spaced from it to prevent such additional waterpercolating back into the reciprocating tube. Such additional water willsaturate or supersaturate the concrete being transmitted and will reduceresistance due to friction. The excess water may be removed at thedelivery end by applying an external suction to a short length of thedelivery hose which is provided with radial perforations in its wall.

The invention may be carried into practice in various ways, but certainspecific embodiments will now be de scribed byway of example withreference to the accompanying drawings, in which:

Figure 1 is a diagrammatic side elevation of a reciprocating pump forwet concrete,

Figure 2 is a cross-section on the line II-II of Figure 1,

Figure 3 is a fragmentary diagram showing a modification in which thereciprocating sleeve is choked, and,

Figure 4 is a fragmentary diagram showing another modification includingan extrusion orifice.

In the embodiment illustrated in the drawings a pump for pumping wetconcrete comprises a fixed tubular pump barrel 10, in the form of aplain steel tube of 2 inches internal diameter and 30 inches length,within which slides a tubular reciprocating pump sleeve 11 of slightlyshorter length. The barrel has a longitudinal slot 12, some 8 inches inlength, formed in its upper wall adjacent one end, and a hopper 13 ofgenerally flattened form is secured to the barrel with its lower endleading into the slot 12. The reciprocating sleeve 11 projects coaxiallyoutof the end 14 of the barrel and is itself formed with a slot 15 some16 inches in length which registers with the slot 12 in the barrel, sothat concrete poured into the hopper 13 will be introduced under gravityinto the interior of the sleeve 11 through the slots 12 and 15. Theprojecting end 17 of the sleeve 11 is closed whilst its other end 18,within the barrel, is open. The outlet end 19 of the barrel, remote fromthe hopper 13, is open and is connected through a flexible hose 20 to asuitable receiver or mould (not shown) for the pump concrete. A circulartongue 21 is mounted within the bore of the sleeve 11 by means of anintegral lug 22 which extends upwardly through the slots 15 and 12 andis secured to the barrel,as shown in Figure 2, so that the tongue 21which is a fairly close fit in the bore of the sleeve 11 divides thebore of the sleeve into two parts, namely a part within the barrel 10,to the right of the tongue as shown in Figure 1, and a part extendingoutwardly to the left of the tongue as shown in Figure 1, beyond therear end 14 of the barrel and beyond the slot 12. The tongue 21 servesto prevent concrete delivered by the hopper 13 through the slot 12 frompassing into the portion of the bore of the sleeve 11 which is to theleft of the tongue-21 as shown in Figure l.

The reciprocation of the sleeve 11 is produced by a combined hydraulicand pneumatic double-acting ram indicated generally at 25, the ramhaving a fixed cylinder 26 Which is mounted coaxially with the barrel10. The ram piston 27 is mounted on one end of a piston rod 28 whoseother end is secured to the end 17 of the reciproeating sleeve 11. Aninlet port 30 formed in the ram cylinder 26 is connected through a pipe31 to a supply of hydraulic fluid maintained under pressure in areservoir 32 of a motor-driven pump 33, and the hydraulic fluid-underpressure is admitted continuously at a slow rate controllableby means ofa valve 34 into the interior of the cylinder 26 on the side of itspiston 27 which is remote from the sleeve 11, so .aslto produce .a slowand substantially uniform advancement of the piston and consequently ofthe sleeve during its forward or pumping stroke in the direction towardsthe outlet end 19 of the barrel 10. An exhaust port 35 of large area isalso provided in the same end of the cylinder 26 and is normally closedby a spring-loaded poppet valve 36.

The return stroke of the sleeve 11, in the direction away from the openend 19 of the barrel 10, is effected by the action of compressed airfrom an air bottle 37 which is permanently connected to an inlet 38formed in the ram cylinder 26 on the opposite side of its piston 27 fromthe inlet valve 30 and outlet port 35, and the action of the compressedair on the piston 27 gives a very rapid acceleration to the sleeve 11 onits return stroke when the hydraulic pressure in the other end of thecylinder is released.

The admission of hydraulic fluid through the inlet 30 into the rampiston continues throughout the return stroke of the piston, but thehydraulic pressure in the cylinder is released during the return strokeby the opening of the poppet valve 36, so as to allow the returnmovement of the piston under action of the compressed; air suppliedthrough the inlet 38. v

The poppet valve 36 is normally held closed by a light valve spring 39acting on a shoulder 40 formed at the end of the valve stem 41. Theopening of the poppet valve 36 is effected by a spring-loaded hammergenerally indicated at 42 and actuated by a connecting rod 43 driven bythe sleeve 11, so that the movement of the sleeve at the end of itsforward or output stroke operates the hammer 42 to open the poppet valve36 and release the hydraulic pressure, thereby permitting the returnstroke of the piston and sleeve to start under the action of thecompressed air.

The hammer 42 comprises a bolt 44 formed with recesses 45 and 46 forengagement by the ball 47 of a springloaded ball catch 48, which permitsthe axial movement of the bolt 44 through a short distance between therecesses 45 and 46. In its rear position, in which the ball 47 engagesthe recess 45, the head 49 of the bolt is just clear of the rear end 40of the valve stem 41, but when the bolt is moved forward until therecess 46 is engaged by the ball 47, the head 49 of the bolt will strikethe rear end 40 of the poppet valve and will move it forwards to openthe valve. The forward movement of the bolt 44 is triggered off by theconnecting rod 43, whose end carries a yoke 50 embracing the bolt 44,and a compression spring 51 surrounds the forward part of the bolt 44between its head 49 and the yoke 50; When the connecting rod 43 is movedforwardly by the movement of the sleeve during its output stroke towardsthe open end 19 of the barrel 10, the forward movement of the yoke willprogressively compress the spring 51 until a point is reached at whichthe force of the spring acting on the head 49 of the bolt 44 overcomesthe ball catch 48, and the bolt 44 flies forwardly to strike the end 40of the poppet valve 36 and to open the valve 36. Forward movement of thebolt is limited by the engagement of the ball catch 48 with the secondrecess 46, so that the valve 36 remains held open. During the last partof the return stroke of thesleeve, the rearward movement of theconnecting rod 43 following the sleeve is transmitted to the bolt 44 bythe engagement of the yoke 50 with a flange 52 formed on the bolt, tomove the bolt back into its rear or cocked position in which the ballcatch 48 engages the recess 45, thereby permitting the valve 36 toclose. The forward end of the connecting rod 43 carries a pair ofadjustable stops 53 and 54, and a yoke 55 rigidly secured to the pistonrod 28 slides along the connecting rod 43 between, the stops 53 and 54tov provide a lostmotion connection between the sleeve 11 land theconnecting rod 43. r A light compression spring 56 is inserted betweenthe yoke 55 and the front stop 54. Thusthe adjustment of the positionsof the stops 53 and 54 along creases the connectingrod .43 enables thelimits of the forward and return strokes. of the sleeve 11 to beregulated, by determining the points at' which the" poppet valve 36 isopened. and iclosed.

In the operation of the pump, during the forward stroke the sleeve 11moves .slowly towards'the' outlet end 19 of the barrel earrying with ita columniof c'oncret'efjammed in its interior, and. thus forcesaheadcfit more. concrete already in thezinterior of the barrel ltlriDuringthisforward movement, .which is producedby the admission of hydraulicfluid to the ram cylinder 26 through the inlet 30, the leading end ofthe sleeve 11 filled with concrete acts as a solid piston, the concretewithin it being jammed solidly by the pressure and by the resultantcumulative static friction of the concrete with the internal surface ofthe sleeve. As the sleeve advances, its empty portion, shown to the leftof the tongue 21 of Figure 1, is progressively moved beneath the hopper13 and is progressively filled with concrete from the hopper.

When the sleeve 11 reaches the end of its forward stroke, the precisemoment of which is determined by the position of the stop 54 on theconnecting rod 43, and by the strength of the compression spring 51 inrelation to the setting of the ball catch 48, the hammer 42 will bereleased to open the poppet valve 36 thus releasing the hydraulicpressure through its exhaust, and permitting the start of the returnstroke under the action of the compressed :air from the bottle 37. Therelease of the hydraulic pressure causes the compressed air to act onthe piston 27 like a hammer blow, snatching the sleeve 11 away from theoutlet end 19 of the barrel, and the inertia forces acting on theconcrete in the sleeve prevent the building up of jamming pressureswithin the sleeve so that slip occurs between the sleeve and theconcrete contained within it and the latter remains more or lessstationary during the return stroke of the sleeve. The newly suppliedconcrete from the hopper 13 is thus embraced by the sleeve in readinessfor the next forward stroke.

This arrangement of the pump permits the adjustment of the length andposition of the stroke of the sleeve, of the speed of the forward strokeand of the acceleration of the rear stroke, and consequently thefrequency of the reciprocation can be adjusted. This enables the pumpingcycle to be regulated to suit the particular mix of concrete beingemployed, in order that the greatest amount of each part of the pumpingcycle may be carried out under the favourable pumping conditionsdescribed above.

In a modification to this embodiment, illustrated in Figure 3, the boreof the sleeve 11, instead of being of uniform cross-section throughout,is provided with a divergent portion 60 leading to a portion of thesleeve at the forward end 18 which is of slightly greater internaldiameter than the internal diameter of the remainder of the sleeve. Thisalteration in the cross-sectional area of the bore of the sleeve, whichmay be as little as 2%, produces a choking action which has a noticeableeffect in initiating the desired jamming action of the concrete in thesleeve during the forward stroke only of the cycle.

In this embodiment an injector tube 61 is provided leading into thestationary barrel 10 near its outlet end 19, and additional water isinjected through the injector 61 into the stream of concrete beingpumped through the flexible hose 20, thereby reducing friction in thehose 20. Excess water is withdrawn from the concrete in the hose 20before it emerges into the mould or framework 62, by means of suctionapplied to a suction pipe 63 lead ing into a suction jacket 64surrounding a short length of the pipe 20 provided with perforations 65.

In the case of a pump whose outlet is fitted with an extrusion orificesurrounding an internalcore, for the purpose of producing an extrudedarticle, a change in the cross-section of the bore of the reciprocatingsleeve would generally be obtained by change in core size, for I 6divergentportion 71 interconnectingits end. portion-72 and a portion. 73which is of slightly: larger cross sectional .area.

WhatI claim as. myinvention and desire to: secure by Letters Patent is:

1. .A pump forpumping .wet concrete in the plastic state, .whichcomprises a hollow reciprocable .tube having an. inlet adjacent one. endand having its other end open asan' outlet leading to areceivenmeans forsupplying the concretetothe interior of the tubethrough the inlet,'andreciprocating means. forcausing. thev tube to reciprocate in .the axialdirection in such. a :rhanner that the linear acceleration given to thetube during-its movement .on its forward stroke towards the receiver isso low that there is little or no slip between the tube and the concretecontained in it during the majority of the forward stroke, whilst duringthe majority of the return stroke the linear acceleration given to thetube is so great that there is slip between the wall of the tube and theconcrete contained in it.

2. A pump as claimed in claim 1 in which the reciprocating tube slideswithin the bore of a stationary outer tube one end of which leads to thereceiver.

3. A pump as claimed in claim 2 in which the receiver comprises a pipeone end of which is secured to the end of the stationary tube.

4. A pump as claimed in claim 3 including means for injecting additional'water into the stream of concrete being pumped near the outlet end ofthe stationary outer tube.

5. A pump as claimed in claim 4 including means for applying externalsuction to a perforated length of the pipe near its outlet end toretifibve, excess water from the stream of concrete being pumped throughthe pipe.

6. A pump as claimed in claim 1 in which the reciprocating meanscomprises a piston in a cylinder, the piston being connected to thereciprocating tube by a piston rod, liquid under hydraulic pressurebeing admitted to the cylinder on one side of the piston to drive thereciprocating tube on its forward stroke.

7. A pump as claimed in claim 6 in which compressed air is admitted tothe cylinder on the other side of the piston to drive the reciprocatingtube on its return stroke when the hydraulic pressure in the cylinder isreleased.

8. A pump as claimed in claim 7 in which the cylinder is provided with apoppet valve which when opened releases the hydraulic pressure, andwhich includes a springpressed bolt arranged to fly forward at apredetermined point in the forward strdlte of the reciprocating tube tostrike the tail of the poppet valve and open it.

9. A pump as claimed in claim 8 in which the bolt is held in its rearposition by a spring-loaded ball catch, and in which a connecting rodsecured to the reciprocating tube increases the forward pressure of thedriving spring on the bolt until at the desired point the ball catch isovercome and releases the bolt, and in which at the end of the returnstroke the connecting rod restores the bolt to its rear position inwhich it is again retained by the ball catch.

10. A pump as claimed in claim 2 in which the concrete is supplied undergravity to the inlet of the reciprocating tube through a stationaryhopper, the inlet to the reciprocating tube comprising an elongated slotwhich is in register with the mouth of the hopper at all points of theforward and return strokes of the tube.

11. A pump as claimed in claim 2 in which the bore of the reciprocatingtube includes a section in which the inside wall of the tube divergestoward the outlet end.

12. A pump as claimed in claim 2 in which an extrusion core extendswithin the bore of the reciprocating tube in the region of its outerend.

13. A pump as claimed in claim 12 in which a portion of the length ofthe extrusion core isof divergent form.

14. The method of using an open-ended hollow tube for pumpingunsaturated concrete through a pipe, corn,

already in the pipe, whereby to propel the latter through the pipe, thelinear acceleration of the tube during such UNITED STATES PATENTS462,313 Gorich et a1. Nov. 3,

Calloway Dec. 20, 1898 654,213 Wilson July 24,

1,288,496 Brosius Dec. 24,

forward movement being sufiiciently low to'avoid slippage 13091878 Y canA i between the tube and its contents due to inertia, and sud- 2'356'829q denly partially withdrawing said tube from the pipe with 10 2378'539Dawlhl June a sufiiciently great degree of linear acceleration to causeslippage between the tube and its concrete contents due to inertia ofthe latter.

